It is known in the waterproofing art to combine a pre-formed waterproofing membrane, such as a rubberized bitumen layer, with a carrier support layer. The carrier support layer may comprise a variety of materials, such as rubber, plastic, and/or metal. It has also been desirable to employ cross-laminated plastic films, such as high density polyethylene, or felts or non-woven sheets as carrier supports for improved stability of the membrane. Such preformed waterproofing membrane laminates are considered "sheet-like" because they are sufficiently flexible that they can be rolled up and transported after manufacture to the job site where they are unrolled and installed on the building surface.
Although such waterproofing membranes provide a considerable improvement in handling and installation when compared to the hot-applied waterproofing of decades ago, the membranes do provide some challenges in that they are often sold in three-foot widths which sometimes makes application difficult. This difficulty is due, in large part, to the tenacity of the waterproofing adhesive.
The preformed adhesive layer of waterproofing membranes are typically protected by a release sheet liner, made of waxed paper or plastic, which may be peeled from the adhesive at the time of application. The use of split, or perforated, release sheets are known in the waterproofing arts. For example, U.S. Pat. No. 4,172,830 of Rosenberg and Gaidis disclosed waterproofing membranes in which release sheets were perforated so that strips could be removed from the adhesive layer, and exposed portions of the adhesive could be overlaid onto the back of an adjacent, installed membrane. This was believed to increase the handling and installation ease of the membranes.
The use of a split release sheet is particularly useful for membrane application in detail areas, such as roof valleys. It is also useful when the membrane is applied as a flashing material around windows and doors, because a portion of the membrane can be affixed into position, while the remaining portion of the membrane is covered by the release sheet and is not capable of fouling (sticking to itself) or prematurely adhering to surfaces.
However, it is quite possible that in some detail areas the use of split release liner sheets can hinder application, since the applicator would have to deal with two portions of the release sheet if he or she wishes to expose at once the entire face of the adhesive layer for attaching the waterproofing membrane to a surface. Pre-split release sheets require that the applicator remove both split portions at once during application on flat (non-detail) areas, and this can make control and accurate placement difficult.
In view of the disadvantages of the prior art, the present inventors believe that a novel waterproofing membrane release sheet liner system is needed.